This undoubtedly exists at some level on the macro scale (servers average salary would be higher if they didn't get tips, or they'd be lower quality). Though ma

This undoubtedly exists at some level on the macro scale (servers average salary would be higher if they didn't get tips, or they'd be lower quality). Though maybe less where everyone gets paid near minimum wage and servers can't be paid less offset by tips. But the micro scale? It would be easy to prove, because drivers can see their base pay and tip. OR the app could lie about the tip or merge it with base pay; then it would be slightly harder, but the driver could still prove by asking customers what they tip.